In the related art, treatment tools having a movable part at a distal end of a bendable elongated insertion part are known as surgical equipment for performing surgical procedures, such as excision of lesions. Additionally, treatment tools which actuate the movable part provided at the distal end of the insertion part with a driving force exerted from a driving source, such as a servo motor, are known. The treatment tools that actuate the movable part with the driving force exerted from the driving source are configured such that the driving force is transmitted to the movable part by a power-transmitting member, such as a wire disposed along the insertion part. The movable part is controlled to make a desired movement on the basis of the amount of displacement of the movable part detected by a detecting part.
U.S. Pat. No. 8,105,338 discloses a treatment tool in which a treatment-tool-side unit and a drive-unit-side unit having a driving source are detachably coupled together. In the treatment tool described in U.S. Pat. No. 8,105,338, an output part of a driving source and an input part to which the output of the driving source is input to the power-transmitting member are detachably coupled together via a coupling.